The present invention relates to a device for simultaneously cutting off two continuous rods of cigarette simultaneously produced by a cigarette-making machine and advancing side by side and substantially parallel to one another along a horizontal surface of the cigarette-making machine itself. In known cigarette-making machines producing a single rod of cigarette, the rod is normally made to advance until it reaches a cut-off region at which it is cut off by the operation of at least one blade carried by a drum of a cut-off device.
The said drum is mounted rotatably about an axis forming an angle with the axis of the rod, which angle is adjustable and is dependent on the length of the cigarette to be obtained. The above mentioned adjustment is necessary in that, as is very clearly explained in British Pat. No. 1 095 970, the blade must advance at the same speed as the rod while the cut is being made.
In a cigarette-making machine producing two rods of cigarette, the problems associated with cutting the rods are very much more complex than those which arise on a single-rod machine.
In fact, in the first place, a two-rod machine is comparable to a machine for the production of a single rod the diameter of which is equal to the inter axis between the two rods increased by the diameter of one of the two rods, and is of the order of 3-4 cm. The cutting of such a rod requires a perfect adjustment of the inclination of the blade-carrying drum in that the time during which each blade remains in contact with the rod is, in this case, very much greater than that which occurs on known machines producing a single rod of cigarette.
In the second place, it is not possible on a two-rod machine freely to position the blade-carrying drum about the rods since there are only two possible positions, that is to say above and below, seeing that only in these two positions are the rods equidistant from the adjustment axis of the drum and are therefore subjected to the same cutting conditions. The said two positions are to be considered as entirely equal to one another even though the embodiment described below of the device according to the invention employs a blade carrying drum above the two rods.
Finally, in a two-rod machine, the region disposed downstream of the cut-off position must remain completely uncluttered in order to permit an operator to intervene on both cut rods and in particular on that rod which is disposed furthest from the operator.
On machines producing a single rod of cigarette it is known to utilise cut-off devices which can be subdivided into two main categories.
In the first category belong cut-off devices (see for example British Pat. No. 324 379) in which the blade-carrying drum is connected to a drive shaft by means of a connection coupling between skew axes constituted by a cardan joint, and the inclination of the drum with respect to the drive shaft is adjusted by means of an arm extending from the drum in a direction opposite that of the drive shaft and carried by a slide movable along a curved guide.
In the second of the categories belong those cut-off devices (see for example British Pat. No. 1 238 459, in which the drum is keyed onto the drive shaft and oscillates together with this latter about an axis relatively spaced from the drum and normal to the direction of advance of the rod.
Known cut-off devices of the first category described above are not suitable to be used on a cigarette-making machine producing two rods of cigarette in that the whole of the device for adjustment of the inclination of the drum is disposed downstream of the cut-off region and would drastically reduce the access to the furthest rod of cigarette.
Known cut-off devices of the second category described above are, on the other hand, not suitable because if they were utilised on the two-rod machine they would not permit the cutting conditions of the two rods to be maintained the same upon adjustment of the inclination of the drum given that this latter oscillates about an axis spaced from the drum itself.